Each year in the United States, rear-end vehicular collisions cause over $18 billion dollars in property damage, cause over 1 million injuries, and over 4000 deaths. The major reason for such collisions is that vehicles travel at separation distances too short to allow sufficient braking time when forward traffic suddenly slows. With the higher percentage of larger vehicles on the roadways, clear view of the road has been increasingly obstructed—further reducing the time a driver has to react to sudden reductions in traffic speed.
There have been many devices in the prior art that have been proposed to reduce the risk of collision. Many of these ideas involve the use of radar. One of the earliest uses of radar to assist with vehicle safety was described in U.S. Pat. No. 2,851,120 issued to Fogiel back in September of 1958, wherein a range finder and calculating device determines a safe traveling distance for the vehicle and applies automatic braking when vehicles move within that range. Numerous subsequent patents such as U.S. Pat. No. 3,898,652 issued August 1975 to Rashid, U.S. Pat. No. 3,710,383 issued January 1973 to Cherry et al and U.S. Pat. No. 3,778,826 issued December 1973 to Flannery et al also combine radar with automatic braking mechanisms. U.S. Pat. No. 5,381,338 issued to Wysocki et al in 1995 and U.S. Pat. No. 6,487,500 issued to Lemelson and Pedersen in November 2002 describe inventions utilizing the global positioning system together with inter-vehicle communications to monitor traffic flow and, in the case of Lemelson and Pedersen, initiate an automatic controlled braking of the vehicle.
U.S. Pat. No. 5,014,200 issued May 1991 to Chundrlik et al and assigned to General Motors Corp., and U.S. Pat. No. 4,621,705 issued November 1986 to Etoh and assigned to Nissan Motor Company each involve systems utilizing radar for automatically controlling vehicle speeds to maintain safe vehicle separation.
Numerous patents involve systems that provide the driver of the vehicle with information about the safe stopping distances between vehicles and other objects. These include U.S. Pat. No. 3,984,836 issued October 1976 to Oishi et al wherein relative distance separations are indicated on an instrument panel, and U.S. Pat. No. 3,850,041 issued November 1974 to Seaman wherein a light beam projected forward of the vehicle indicates the required safe stopping distance. U.S. Pat. No. 5,357,438 issued October 1994 issued to Davidian describes a device which includes a speed sensor, a space sensor, and a control panel with means to input parameters concerning the vehicle, the condition of the road, the daylight condition, and even a ‘condition-of-driver’ parameter each used to help calculate a ‘danger-of-collision distance’ to nearby objects.
And U.S. Pat. No. 5,369,591 issued to Broxmeyer in 1994 describes a system for ‘longitudinal control and collision avoidance’ wherein magnets are embedded in both the roadway and the vehicle with position sensors broadcasting by radio the vehicle's position to local receiving stations and then receiving, in return, an audio feedback command for directions for safe maneuvering.
U.S. Pat. No. 5,504,472 issued to Wilson describes a device that monitors the pressure a driver applies to their brake pedal, and a when a high value is detected, flashes the vehicle's brake light to warn trailing drivers.
Each of the above mentioned patents—together with numerous other patent variations not listed above—may be successful in meeting their stated objects to some degree. However, none has yet to be successfully integrated into today's vehicles and roadways to any significant extent because they either involve technology that is too complicated, or propose implementing systems that are not financially viable for society at this time, or are systems which are activated by the wrong parameter. In the patent issued to Davidian, for example, a ‘danger-of collision distance’ parameter is used and when the measured distance of an object is equal to or less than this value, a collision alarm is activated. The fallacy in using distance as a parameter for activating an alarm is that the traffic patterns vary so frequently when driving that it becomes a useless parameter to monitor. For instance, when a safe ‘danger-of-collision distance’ is computed for a vehicle traveling at 60 miles per hour, the value may be useful to apply when a vehicle is traveling down a sparsely traveled highway—for the alarm will notify the driver when an object is closer than this distance—however, when the same vehicle then encounters a dense traffic pattern the distance separating vehicles may always be shorter than the ‘danger-of-collision’ distance in which case the alarm will always be activated. The system then fails to be able to provide any new information when a sudden speed change occurs. When vehicles are traveling almost bumper-to bumper at full highway speed, then it becomes even more imperative that the speed change be the deciding parameter to convey to a trailing vehicle-not the distance. If, alternatively, the ‘danger-of-collision’ distance is set to a shortened value for dense traffic, then the moment the traffic opens up, the shortened distance will no longer give warnings about speed changes beyond that distance proving to be a liability to the driver expecting a warning. Another problem with using distance as the deciding parameter to activate a warning is that consecutive vehicles may be adjusting their speeds at the same rate in which case their relative separations may remain constant-masking the fact that the forward traffic is also slowing.
In summary, the danger from collisions on the roadways has not been alleviated by any of these prior art inventions. Ironically, despite the plethora of innovative ideas within the patent records, the best mechanism which exists today for alerting a driver of changes in the forward traffic flow are(is) the standard brake lights found on all vehicles-and this prior art feature has been incorporated into vehicles for over 80 years.
The prior art in brake lights, however, has four inherent deficiencies that can contribute to the problem of vehicular collision. First, they require the driver of the vehicle to observe the sudden change in speed in the forward vehicle. If the driver is not paying attention to the roadway, or does not have good visibility of the forward roadway, then they may not apply the brakes—and activate the vehicle's brake light—until much of the free space forward of the vehicle has been traversed. Secondly, the driver must use their judgment to decide whether the traffic speed change warrants applying their brake. Often a driver's judgment is incorrect and the brake lights are not activated until a collision becomes imminent. Thirdly, there can be a loss of a half-second or more due to the reaction time between the instant when even an alert driver recognizes a change in speed in the forward vehicle and the moment when the driver actually applies the brake activating their brake light. And fourthly, frequently the driver of a vehicle may be resting their foot on the brake pedal or lightly applying the brake and falsely indicating to the driver of a trailing vehicle of a reduction in speed-and eliminating the opportunity to later initiate a meaningful braking warning.
Although it is the speed changes that are most important to a driver, there existed no viable alternative to the operator-initiated prior art brake light for communicating information about the speed of a forward vehicle to the driver of a trailing vehicle until U.S. Pat. No. 7,162,369 issued to Thorne in January 2007 titled: SPEED-MONITORING RADAR-ACTIVATED BRAKE LIGHT. 
Thorne teaches incorporating a radar device into a host vehicle that monitors the speed of a forward vehicle and automatically alerts the driver of a trailing vehicle when that forward vehicle decelerates. Because that device operates automatically without dependence on the driver's level of attentiveness or the speed of their reactions, it alerts trailing drivers of the need to brake at least a half-second sooner than any prior art brake light device. At freeway speeds, that typically gives trailing drivers an extra fifty feet to avoid a collision.
Accordingly, one or more examples of the invention have one or more of the following objectives, features and advantages:
(a) to provide a radar-activated, speed-monitoring device, integral with a host vehicle;
(b) to provide an improved method for enjoining a radar-activated, speed-monitoring device with existing prior art brake lights and a modified way for activating those lights such that trailing drivers can be alerted to potentially hazardous changes in vehicles forward of the host vehicle;
(c) to provide an improved method for enjoining a radar-activated, speed-monitoring device with a new dual acting form of brake light and a modified way for activating those lights such that trailing drivers can be alerted to potentially hazardous speed changes in vehicles forward of the host vehicle;
(d) to provide an improved method for a warning signal which can better capture the attention of trailing drivers to potentially hazardous speed changes in vehicles forward of the host vehicle;
(e) to provide a method whereby a radar-activated, speed-monitoring device can convey the rate of deceleration in the warning signal provided to a trailing driver;
(f) to teach how such a speed-monitoring radar-activated brake light can be uniquely incorporated into existing vehicles without major alteration to a vehicle's existing brake light system.
Further features and advantages of this invention will become apparent from a consideration of the drawings and the ensuing description.